@Riker most of them are capital english letters in case you couldn't tell :| one of them is lowercase a and most of the others are greek. in fact, the first paragraph tells you what each type of symbol means

Lay out the Carpet
code-golfascii-artstring
Inspired by this SO question.
Challenge:
Input:
A string \$s\$
A character \$c\$
Output:
Create a diamond-square ASCII art of the string in all four directions, with the first character of the string in the center and going outwards. Which is i...

Multiplicative Persistence
Multiply all the digits in a number
Repeat until you have a single digit left
As explained by Numberphile:
Numberphile "What's special about 277777788888899?"
Numberphile "Multiplicative Persistence (extra footage)"
Example
277777788888899 → 2x7x7x7x7x7x7x8x8x...

@Rick iirc, a powerful integer n is one such that, if a prime p divides n, then p² also divides n. Perfect powers, on the other hand, are numbers whose prime factors are all the same. So, 8 is both powerful and a perfect power, since 8=2³ (perfect power); also 2 is the only prime divisor of 8 and 2² also divides 8, so 8 is a powerful number.

There's a visual method for multiplication that is taught to Japanese schoolchildren [citation needed] that uses lines and crossings to get the answer.
Image Source
Your task is to implement this in ASCII art. You will be given two numbers to multiply. The output should be the corresponding A...

@J.Sallé would you say for a positive integer n to be powerful but not a perfect power, would it be safe to say the decomposition of a that number whose gcd is = 1 for example 36 [2,2,3,3] and it's gcd is = to 1

An Achilles number is a number that is powerful but not a perfect power. A positive integer n is a powerful number if, for every prime factor p of n, p2 is also a divisor. In other words, every prime factor appears at least squared in the factorization. All Achilles numbers are powerful. However, not all powerful numbers are Achilles numbers: only those that cannot be represented as mk, where m and k are positive integers greater than 1.
Achilles numbers were named by Henry Bottomley after Achilles, a hero of the Trojan war, who was also powerful but imperfect. Strong Achilles numbers are Achilles...